TWI353966B - Process for recycling waste acid - Google Patents

Description

1353966 IX. INSTRUCTIONS OF THE INVENTION: TECHNICAL FIELD OF THE INVENTION The present invention relates to a recycling process for converting spent acid from a variety of industrial processes into useful commercially valuable products, including magnesium sulfate. In particular, the method converts spent sulfuric acid classified as RCRA hazardous waste into products for sale, including fusible metal oxides and magnesium sulfate. [Prior Art]

Sulfuric acid has been used in hundreds of industrial applications ranging from metal surface treatment to food manufacturing. Some uses include pickling processes, refining 'fertilizer manufacturing, paper & paper manufacturing' and are used in the manufacture of printed circuit boards, semiconductors and lithograph wafers. In fact, sulfuric acid is the most widely used chemical in the world, and the United States consumes more than 38 million a year. Most, if not all, of these sulphuric acids produce large amounts of spent sulphuric acid containing all types of inorganic and organic contaminants. The waste sulfuric acid is treated by a regeneration method, which comprises injecting sulfuric acid into a combustion furnace to produce sulfur dioxide (s〇2). This s〇2 is then converted to sulfur trioxide (so3) and finally absorbed in 98% sulfuric acid to obtain 99% or more of pure sulfur. The method of β Hai et al. is disclosed in U.S. Patent No. 6,399,. One of the major drawbacks of the treatment methods is the large amount of energy and the costs associated with thermal decomposition. Other known treatment methods include treatment with CaCOd Ca0 to neutralize sulfuric acid and form usable gypsum (CaS〇 4.2 (H2(7)). Gypsum is used in cement, clear water, stucco and several other products. For example, US Patent No. No. 6,099,814 discloses a method for obtaining a secondary product of magnesium sulfate by using CaC〇3 in a scrubber. The problem with these types of processes is that a large amount of gypsum is produced by J238J6.doc which is required for the product. These methods are limited to the fact that the spent acid that can be used must not contain metal contaminants commonly found in spent acid streams, such as copper, iron, lead and other metals that will precipitate with the gypsum to avoid low value or no value. In another treatment, the waste rock IL acid is used to form iron oxide pigments (see U.S. Patent No. 6,53, 987). Because of the large amount of dangerous waste acid (such as sulfuric acid) produced each year. Therefore, there is a need for a simple and efficient recovery method to convert such spent acid streams into useful and consumable products. It is apparent from the following description and the scope of the patent application, The method can achieve the object. [Disclosed] The invention does not provide a controlled manner to contact with a large amount of magnesium-containing magnesium compound (preferably oxidized (Mg)). Iron is added as a separate compound to the spent sulfuric acid. By controlling the positive value and temperature of the mixture formed when the magnesium compound is added to the spent acid, an aluminum oxyhydroxide and a ferric hydroxide iron floc are formed. The floc is mixed with and reacts with various kinds of dyes of the waste acid solution. The contaminants or impurities are usually =, recorded, steel, complex, bismuth, gallium and may include a large amount of various organic substances. The oxyhydroxide hydroxide and oxyhydrogen oxyhydroxide required for the pollutants are formed under different positive values, and the floc formed each time is responsible for removing various pollutants. At the same time, the addition of the (tetra) compound also leads to Mg and Separation from sulfuric acid $ ςη -2 β # 曰

... form a town of sulfuric acid. When the PHI-degree... should be completed, the sulfuric acid lock solution and the floc mixture are mixed. 123816.doc: tJ can be processed to obtain a high-quality f MgSG4 solution. The sorghum metal oxide or hydroxide product that can be processed from the 73⁄4 遽 process, (4) (4) (iv) ^ operation. More specific $ refining method includes: the method of treating the contaminated liquid by inorganic and organic impurities, the combination of η方沐, 4, mx ^ / 10000 including U, the following steps: A spent acid of a compound of the group consisting of: sulfuric acid, sulfuric acid steel, iron sulfate organic hydrazine (such as acetic acid), and inorganic acids (such as squaric acid, methyl sulphate) and combinations thereof, which contain a group selected from the group consisting of the following Impurities: arsenic, antimony: chromium chrome, antimony, gallium, at least one organic compound and mixtures thereof; formed by contacting the spent acid with a metal-containing Mg compound containing a heart and iron

Starting with a mixture having a pH of less than 5; measuring and monitoring the pH of the mixture; agitating and maintaining the mixture at a temperature of from about ambient to about 9 rc_; by forming an iron oxyhydroxide, oxygen hydride selected from a floc composed of a group of aluminum oxide, copper oxyhydroxide and a mixture thereof misaligns impurities contained in the spent acid via flocculation; increasing the pH of the mixture by continuously adding a Mg compound to the mixture until obtained A pH value of 5 or higher; and separating the floc containing impurities from the mixture by filtration or other solid liquid separation method to separate the solution containing magnesium sulfate. Another embodiment of the present invention comprises a method of treating a spent acid solution contaminated with inorganic and organic impurities, the method comprising a combination of the steps of providing a salt selected from the group consisting of sulfuric acid, an organic acid (such as acetic acid), and a mineral acid (such as phosphoric acid, a compound of the group consisting of methanesulfonic acid) and combinations thereof, and also containing a waste acid selected from the group consisting of ruthenium, iron, copper, shishen, chrome, smect, gallium, at least one organic compound, and mixtures thereof Forming by contacting the waste stream with a metal Mg compound containing aluminum and iron base 1238l6.doc 1353966 (such as Mg 〇, Mg(OH) 2, MgC03, MgC03, XMg(OH) 2 or any similar substance) Initially having a mixture having a pH of less than 5; measuring and monitoring the pH of the mixture; agitating and maintaining the mixture at a temperature ranging from about ambient to about 97 ° C; adding the Mg compound until the pH of the mixture is greater than 2; forming iron oxyhydroxide floc; using iron oxyhydroxide floc to make the waste acid impurities mismatch while maintaining the pH of the mixture is greater than 2; raising the pH of the mixture to above 3.5; forming oxygen Oxidizing the floc; aligning the spent acid impurities with the aluminum oxyhydroxide floes; increasing the pH of the mixture by continuously adding the Mg compound to the mixture until a pH of 5 or higher is obtained; The mixture is used to determine the copper content; the specific gravity of the mixture is measured; and the mixture is filtered to remove the miscible impurities and floes to form a purified magnesium sulfate solution. [Embodiment] Although Figure 1 depicts only one of many possible embodiments, the method flow shown is suitable for describing the recycling of the present invention. The spent acid containing sulfuric acid (HjSO4) is first added to the storage tank 1 via line 2. Waste acid as used herein means a residue or effluent stream containing ΗΑ〇4, free s〇2, S〇3 or so4·2 and having a pH of less than 5, more preferably less than 1. Further, the spent acid may also include other acids such as organic acids such as acetic acid and inorganic acids such as phosphoric acid and methanesulfonic acid. The spent acid typically additionally includes a variety of contaminants such as copper, arsenic, antimony, chromium, antimony, gallium, and organic compounds. Although the exact composition of the spent acid depends on the source and the initial method of using succinic acid, the spent acid preferably has the following composition range: 1% to 99.4% sulfuric acid (H2S〇4), and the treated concentration is more usually present. The range of ΗΑ〇4 is in the range of 4.0% to 77%. The spent acid may contain a wide range of inorganic contaminants such as, but not limited to, Ag, Ba, Ca, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. The concentration of such inorganic contaminants will be in the range of as low as 0.000189% up to n 4%. Organic pollutants will also be present, and the total amount will be in the range of 0.026% to 33,600% based on c〇D (chemical oxygen demand). Other inorganic impurities will generally be present, such as nitric acid (HN〇3) in the range of 0.000043% to 1.2% and hydrogen peroxide (h2〇2) in the range of 0.084% to 1.61%.

Some or all of the spent acid may be used in other processes (such as for tin removal operations) prior to the addition of spent acid to the sump, where spent acid may be used to clean the tin-removed metal and then recycle the metal to the end. (such as a melting furnace). In either case, once the amount and composition of the spent acid is known, the stoichiometry of the magnesium compound is determined based on the concentration of S〇4 2 in the spent acid to maximize its formation. The magnesium compound used in the present invention is not critical and may be selected from the group consisting of MgO, Mg(0H)2, Mg(c〇3)2 and mixtures thereof. Magnesium compounds containing vapor or nitrogen compounds are not ideal. Alternatively or additionally, a waste stream containing a relatively high concentration of Mg + 2 may also be used. Particularly preferred: sedation: The source of the material is MgO, and in particular is a heart palpitus containing a measurable iron reduction. A typical MgO composition comprises from about 92 to about 97% by weight of Mg〇; from about 2 to about the weight. /. And about 0.2 to about i% by weight of Fe, more preferably about 6% by weight

The state s seri Ping father needs J more A1 or Fe. Due to the complexity of such spent acid, it is best to use the experiment of individual spent acid. Additional additions may be added directly to the acid in the form of a ruthenium or in the form of its corresponding sulfate. 123816.doc As described below, the method includes, and is important to, because the metals form oxynitride floes that are chelated and mismatched with contaminants contained in the spent acid. When the floc and the floc are formed, the contaminants are removed from the magnesium sulfate solution formed by the addition of the magnesium compound. If the magnesium compound used does not contain Fe and/or A1 compounds sufficient to form the necessary oxygen oxide floc, other sources of iron and/or aluminum compounds may be added to the storage tank as separate compounds. Preferably, the compounds will include sulfuric acid peaks l2 (S〇4) 3) and iron sulfate (FeS〇4). Regardless of the manner in which FeW is added to a mixture of spent acid and magnesium compounds, both metals are necessary so that iron oxyhydroxide flocs and oxygen oxygen (tetra) floes can form and coprecipitate, absorb, and mate. And/or condensing the contaminants in the mixture, such that the contaminants are removed from the solution by the reaction of Mg, S〇4-2. Preferably, the town (4) is metered into a human tank 1+ to ensure that a homogenous person is produced. Figure 1 depicts a possible method of adding magnesium (4) using hopper 4 and weighing configuration 5. Other methods are also possible, such as the use of an injector system combined with U for accurate addition. In the case where it is necessary to add independent / Γζ: one thing, the method of adding the same kind of compound can be used, and it is very necessary to fully transfer the material to ensure the town of sulphuric acid. Effectively formed: licensed to provide intimate contact between Mg, sub and s〇, 2 ions. Lu Luzhi, as shown in Figure 1, is a mixture of finds. Similarly, the two objects 6 contribute to agitation by holding the door-like compound in the sump 1 via the pipes 7, the pumps 8 and 1〇. In addition, the 偾 Shield exhibition will be in addition to the figure! It is shown, but can be used in the recycling of I238I6.doc:: static mixing in the pipeline to provide the magnesium compound and the waste acid is also intense. The reaction between the heat and the auxiliary (4) and S〇42 is also used. Initial counter: Provides sufficient heat' however, as the reaction proceeds, it must be added from an external source. Similarly, the ambient temperature can more or less control the external heat addition. A better way to add heat is to use the in-pipe heat exchanger. It is necessary to maintain the mixing degree at about ambient temperature to about 97t, preferably about 85. . (: to about 97 ° C. Flocculation of the oxyhydroxide necessary to form contaminants from the mixture is required for pH monitoring and control. The pH of the spent acid is usually initially, ', 1, or less. When the pure compound is added, the pH starts to rise. The positive value of the mixture sample is measured using the known and measured (four) period or continuously. The formation of the oxygenated iron oxide floc will begin with the iron floc. The formation acts as an effective adsorption for the trioxide, complex, fault, recording and various organic substances. The compound does not inherently contain iron, and the iron compound is added before the pH value of about 2.2 is reached. Iron sulphate). Once it is noted that there is no soluble iron in the solution, this means condensate. When more basic magnesium compounds are added to the mixture, the pH begins to rise: at a pH of about 3.8. The formation of oxyhydrogenated flocculant begins. Like the iron oxyhydroxide floc, the aluminum oxyhydroxide floc is an excellent flocculant for removing various contaminants not removed by ferric oxyhydroxide. If the town compound does not contain enough or does not contain enough chains, then In addition to the lock compound, an alternative source such as sulphate can be added independently. In addition, we have been surprised to find that the oxyhydroxide chain (4) also removes any of the remaining amounts of 4-1. ☆ Remove other impurities. I238l6.doc 1353966 It is very important to make high quality magnesium sulphate floc. This is because even a trace amount of iron will discolor the magnesium sulfate solution. Even if it is as low as iPPni, it will give a yellow color and 5 PPm. Turbid appearance. In fact, color is the key quality control variable. This method results in a water white sulfuric acid solution with a color analysis of the maximum value of APHA 30. Therefore, the use of oxyhydroxide to remove any traces of oxygen oxidation Iron is key.

Further, when more town compounds are added to the storage tank i, the positive value continues to rise until a pH of about 5 is reached. At this point, the addition of magnesium compounds should be slowed or stopped and carefully monitored? 11 values and temperature. At a pH of about 5.3, any copper ions present in the mixture will begin to precipitate and are about. Completely removed from the sulfuric acid solution at a pH of 67. Analysis of Sulfuric Acid Solutions Copper and other metals will confirm the need to add additional town compounds. Preferably, the heavy metal eyebrow I c metal 3 I is less than 5 ppm; the total content of selenium, cadmium and lead is less than 3 PPm; and the total content of Shi Shen, Lu, wrinkle, Gu, Lu, Luo, Meng is less than 15 PPm . It is also necessary to reach a pH in the range of 6 to 9.2. After reaching a pH of 5 to 6, it may be necessary to stop adding the cationic compound to avoid the formation of an oxysulfate (〇XySUlfate). These oxygenated sulfates are easy (4) because they are similar in composition to rock. Alternatively, a chlorine oxidation lock (Mg(〇H)2) may be added to the storage tank 1 to further increase the pH within the desired range of 6 to 9 2 . Once the desired pH is reached, a mixture of magnesium sulfate and flocculated contaminants, & is removed from storage tank 1 by g channel 11 and transitioned to separate the sulfuric acid solution from the unpainted, condensate. It is not critical to the method, and any known solid-liquid method can be used, such as vacuum filtration or centrifugal separation. It is better to use the pressure filter to finely monitor the machine fluorine #王12. The resulting filter cake 13 can be processed (e.g., by heat treatment) to obtain a metal oxide solid which can be sold to a metal refinery for use in a refining process. Through its design. The object ' i / t # 1 ^ a ^ g lane 1 4 from the seventh (2) concentration (four) liquid in the range of (four) to 27% by weight and delivered to the storage device. Depending on the desired end of the sulphur bismuth magnesium: ' can be used, for example, using ultraviolet (UV) light exposure and / or carbon filtration: two = treatment. These additional refining treatments remove any traces of soluble inorganic compounds and organic compounds that are not flocculated or removed in the second. Medium: Many of the differences in prior art methods for the treatment of spent acid streams do not use any of the compounds of the formula (iv). In fact, it will result in the formation of a gypsum product which will be condensed with iron oxyhydroxide and hydrogen oxyhydroxide (tetra) to result in two:)' and due to the heavy metal content of the starting spent acid. In fact, in certain cases it may be necessary to step up to remove any traces of calcium. In addition, the filtration process is greatly increased and requires a stronger solid processing capability. Therefore, this method does not add any mom compound. According to the example, the waste acid with the following contents is treated, so that tfj quality sulfuric acid and L k town are produced from waste sulfur. The first step is to deposit the iron hydroxide by adding magnesium oxide, and then continue to add the free/cerium oxide until the soluble iron and the soluble aluminum are coprecipitated, and the inorganic and organic impurities are removed from the obtained sulfuric acid town. Waste acid (before treatment): show) inorganic impurities (in parts per million)

Cd Cr 1,250 ppm 10 123816.doc 1353966

Cu . • ........... '····· .1,200 Μη . •.............. . . . . 20

Ni . . . . . . . . . . . . . . . . .

Zn . . . ............. 10 l Organic impurities (expressed as chemical oxygen demand). COD ........ ........ ....······ 1,250 ppm After the iron precipitation, the flat rod slave is ordered, and the above impurities have been reduced to j; the lower content: y impurity modified content \ reduced percentage

Cd 390 ppm, -68.5%

Cr · · . . . . . -100%

Cu........0.0 -100% Μη....... 〇.〇 -100%

Ni........7.0 -94.3%

Zn........〇.〇-100% Total organic matter expressed by C〇D....390 _68 5% Using the same feed as above, it is guaranteed to hold a constant and Pre-precipitation, in the solution, 21% of the solution, and then add the pores of magnesium to precipitate iron and aluminum. We found that the cd content decreased to 280 ppm, which was lower than the initial content. . It is to be understood that the embodiments and examples disclosed herein are provided for illustrative purposes only, and that the various combinations of the methods, including the methods, will be suggested to those skilled in the art. Widely explained: I238l6.doc 14 1353966 [Schematic Description of the Drawings] Figure 1 is a schematic process flow diagram showing one embodiment of the recycling method of the present invention operating in a batch operation. [Main component symbol description] 1 Storage tank 2, 3, 7, 11, 14 Pipe 4 Hopper 5 Weighing configuration 6 Mixer 8 Pump 9 Heat exchanger 10 Return pipe 12 Filter press 13 Filter cake 123816.doc - 15 -

Claims (1)

X. Patent application scope: A method for treating a waste acid solution contaminated by inorganic and organic impurities, comprising a combination of the following steps: , a) providing a combination selected from the group consisting of sulfuric acid, copper sulfate, iron sulfate, acetic acid, and scorpion a compound of the group consisting of an acid and a combination thereof, and also a spent acid selected from the group consisting of sputum, chromium, strontium, gallium, and copper, at least one organic compound, and mixtures thereof; b) by making the waste The acid is contacted with a compound containing aluminum and iron to form a mixture having an initial pH of less than 5; C) measuring and monitoring the pH of the mixture; d) a temperature ranging from about ambient to about 97 〇C Stirring and maintaining the mixture; ^ ' e) forming a floc selected from the group consisting of iron oxyhydroxide, oxyhydrazine oxide oxyhydroxide, and mixtures thereof by flocculation to make the spent acid contained therein Contaminant mismatch; f) increasing the pH of the mixture by continuously adding Mg compound to the mixture until a pH of 5 or higher is obtained; and using a filtration process to cause the inclusion of such contaminants The Flocs separated from the mixture, thereby separating the solution containing magnesium sulfate. 2. The method of claim 1, further comprising analyzing the spent acid to determine a sulfate concentration. 3. The method of claim 2, further comprising determining a stoichiometry of Mg required to react with the sulfate to form magnesium sulfate. 4. The method of claim 1, further comprising adding a Mg compound comprising a solid form of at least 95 weight 0/〇 123816.doc 5. Mg〇. 6. The method of claim 1, which is carried out - and is isolated into the spent acid. As in the method of claim 1, the compound is further reacted and recycled. The step comprises metering the Mg compound into the step comprising using a mixing tank to stir up the method of borrowing and reclaiming during the recycling period, 哕., f entering the team x ^ 0 甘行倨期Oh... The matter is maintained by the heat exchanger. 8. As claimed in the method, 苴, #1 叨 / / degree. Include treatment __(d) to = any organic compound present in the spent acid 9_ as requested in item 8, and enter a sulphuric acid record 〜* Progress includes the use of UV irradiation to remove organic contaminants from the magnesium sulphate . 1 〇. As in the method of claim 8, 1 , . ', the magnesium sulfate solution is carbonized in one step to remove organic contaminants. 11. A method for treating an inorganic and organic contaminated material, a selected 4_ another micro-π wood/dyeable spent acid solution, comprising a combination of the following steps:) providing a content selected from the group consisting of sulfuric acid, acetic acid, phosphoric acid, and a compound of the group consisting of a combination of a sulfonic acid and a pot, and also containing a spent acid selected from the group consisting of: m 锑: steel, chromium, lanthanum, gallium, at least one organic compound, and mixtures thereof; The spent acid is contacted with a Mg compound and a compound containing aluminum and iron to form a mixture having an initial pH of less than 5; c) measuring and monitoring the pH of the mixture; d) at about ambient temperature to about 97 ° C Stirring and maintaining the mixture at a temperature within the range; 123816.doc 1353966 e) forming a floc selected from the group consisting of iron oxyhydroxide, aluminum oxyhydroxide, oxyhydroxide, and mixtures thereof by flocculation The contaminants contained in the acid are mismatched; • f) increasing the pH of the mixture by continuously adding Mg compound to the mixture until a pH of 5 or higher is obtained; ) by using a filtration process The floc having the contaminants is separated from the mixture to separate the solution containing magnesium sulfate; and φ h) forming a filter cake containing the floes in the filtration process, and drying the filter cake to form A solid product containing a metal oxide suitable for recovery in a smelting process t. 12. A method of treating a spent acid solution contaminated with inorganic and organic contaminants, comprising a combination of the following steps: a) providing a content selected from the group consisting of sulfuric acid a compound of the group consisting of acetic acid, phosphoric acid, methylene acid, and combinations thereof, and also containing a group selected from the group consisting of calcium, iron, arsenic, antimony, copper, chromium, antimony, gallium, at least one organic compound, and mixtures thereof a spent acid; b) forming a mixture initially having a pH of less than 5 by contacting the waste stream with a Mg compound comprising iron and aluminum; c) measuring and monitoring the pH of the mixture; d) Agitating the mixture at a temperature ranging from about ambient temperature to about 97 ° C and maintaining the mixture; e) adding the Mg compound until the pH of the mixture is greater than 2; f) forming iron oxyhydroxide floes; g) Using the ferric oxyhydroxide floes to make the waste acid contaminants 123816.doc 1353966 "while maintaining the pH of the mixture greater than 2; h) raising the pH of the mixture to above 3.5; i) forming oxygen Aluminum hydroxide floc; j) aligning such spent acid contaminants with the aluminum hydroxide floes; ] <_) increasing the pH of the mixture by continuously adding Mg compound to the e-xuan mixture Until a pH of 5 or higher is obtained; l) the mixture is analyzed to determine the copper content; m) the specific gravity of the mixture is measured; and η) the mixture is filtered to remove miscible contaminants and floes to form sulfuric acid Magnesium solution. The method of claim 12, further comprising the step of treating the magnesium sulfate solution 1238l6.doc